43 6 Memoir Sears Foundation for Marine Research 



lap, with the margin of the jaw interrupted at the point where the maxillary passes over 

 the premaxillary. In related genera {Odontognathus and Opisthopterus) these bones are 

 separated by a membranous toothless section, with the margin of the upper jaw con- 

 tinous. The genus differs further from the other genera that lack the pelvic In having 

 fewer anal rays. 



Range. Known from two species, N. tropicus from the Pacific coast of Panama 

 and Peru and cubartus from Cuba. 



Neoopisthopterus cubanus Hildebrand 1948 

 Figures 112, 113 



Study Material. Six small specimens, 43— 50 mm TL, 35-41 mm SL, apparently 

 young adults not fully mature; collected at Havana, Cuba, and sent to the writer by 

 Dr. Luis Howell-Rivero of the Museo Poey at Havana; USNM 143569 and 



143570- 



Distinctive Characters. N. cubanus is very closely related to N. tropicus Hildebrand 

 {57'- 94> %• 19)) known from Panama and northern Peru, from which it differs only 

 in having somewhat fewer dorsal and anal rays {cubanus: D. 13 or 14, A. 39—43; 

 tropicus: D. 14—16, A 43—48). Also, these fins are somewhat differently placed; in 

 cubanus the dorsal originates slightly more than an eye's diameter behind the beginning 

 of anal and about equidistant between the margin of the opercle and the base of caudal, 

 whereas in tropicus it begins scarcely an eye's diameter behind the origin of anal and is 

 about equidistant between the posterior margin of the eye and the base of caudal. The 

 average number of gill rakers on the lower limb of the first arch apparently is lower 

 in cubanus than in tropicus (respectively, 17—19, 18—21). This, then, is another instance 

 of the rather common occurrence of "twin" species in the Atlantic and Pacific, gener- 

 ally found on the opposite coasts of the Isthmus of Panama. As the West Indian and 

 Atlantic Panamanian faunas are largely identical, cubanus may be expected on the Atlan- 

 tic coast of Panama and neighboring countries. 



Description. Proportional dimensions in per cent of standard length, and counts, 

 based on study specimens 35—41 mm SL. 



Body: depth 17—21. Anal fin: length of base 33—39. 



Caudal peduncle: depth 6.5—8.5. Distance from snout to origin of: dorsal 

 Head: length 21.5-23.5; depth 18.5- 60-64. 



20.5. 



Snout: length 5.3-6.8. Scales: lost, ca. 43 pockets. 



Eye: diameter 5.5-6.8. Ventral scutes: 23-28. 



Interorbital: width 2.6-3.1. Fin rays: dorsal 12-14; anal 39 to 43; 

 Maxillary: length 13.2— 14.8. pectoral 13. 



Mandible: length 12.8— 13.7. Vertebrae: 47 (i specimen). 



